To be able to sell or give gift vouchers so that they can be used later in future purchases.
This voucher will have a balance that will decrease with each purchase.
Example 1: I sell a voucher for 100€ and then when I make a new sale, I can apply the voucher as a discount.
Example 2: They return an item to me but I don't give it a refund, but I give it a voucher for future purchases.